1. Field of the Invention
The present invention is directed to purified and isolated RTVP-1-G1iPR-like polypeptides (“RGL polypeptides”) and fragments thereof, the nucleic acids encoding such polypeptides, processes for production of recombinant forms of such polypeptides, antibodies generated against these polypeptides, fragmented peptides derived from these polypeptides, and uses thereof. In particular, the invention relates to compositions and methods for the detection, treatment and prevention of metastatic and other neoplastic disorders.
2. Description of Related Art
Cancer cells may be are defined by two heritable properties, uncontrolled growth and uncontrolled invasion of normal tissue. A cancerous cell can divide in defiance of the normal growth constraints in a cell leading to a localized growth or tumor. In addition, some cancer cells may become metastatic, gaining the ability to migrate away from their initial site and invade other tissues areas and types. It is the combination of these two features that make a cancer cell especially dangerous.
An isolated abnormal cell population that grows uncontrollably will give rise to a tumor or neoplasm. As long as the neoplasm remains non-invasively in a single location, it is said to be benign, and a complete cure may be expected by removing the mass surgically. A tumor or neoplasm is counted as a cancer if it is malignant, that is, if its cells have the ability to invade surrounding tissue. True malignancy begins when the cells cross the basal lamina and begin to invade the underlying connective tissue. Malignancy also occurs when the cells gain the ability to detach from the main tumor mass, enter the bloodstream or lymphatic vessels, and form secondary tumors or metastases at other sites in the body. The more widely a tumor metastasizes, the harder it is to eradicate and treat.
As determined from epidemiological and clinical studies, most cancers develop in slow stages from mildly benign into malignant neoplasms. Malignant cancer usually begins as a benign localized cell population with abnormal growth characteristics called dysplasia. The abnormal cells acquire abnormal growth characteristics resulting in a neoplasia characterized as a cell population of localized growth and swelling. If untreated, the neoplasia in situ may progress into a malignant neoplasia. Several years, or tens of years may elapse from the first sign of dysplasia to the onset of full blown malignant cancer. This characteristic process is observed in a number of cancers. Prostate cancer provides one of the clearest examples of the progression of normal tissue to benign neoplasm to malignant neoplasm.
Prostate cancer is the most common malignancy in men in the USA, resulting in an estimated 41,800 deaths in 1997. (Parker S L, et at, CA Cancer J. Clin. 47: 5-27, 1997). The widespread use of prostate-specific antigen (PSA) has dramatically increased the number of patients diagnosed with prostate cancer and generally lowered the stage of disease at diagnosis. (Scardino P T, Urol. Clin. N. Am. 16:635-655, 1989; Epstein J L, et al., JAMA 271: 368-374, 1994). Nevertheless, 5%-10% of cancers detected by PSA screening are clinically advanced and not candidates for radical prostatectomy. Despite surgical removal of the prostate, 30%-60% of men treated will have recurrence of cancer within 5 years, suggesting that the clinical stage of the patients undergoing surgery was highly inaccurate. 20%-57% of patients undergoing definitive surgery with presumed localized disease will have rising PSA following treatment, also indicative of local or distant residual disease. (Ohori M, et al., J. Urol. 154: 1818-1824, 1995; Zeitman A L, et al., Urology 43: 828-833, 1994). Neither of these conditions is amenable to curative therapy.
The walnut-sized prostate is an encapsulated organ of the mammalian male urogenital system. Located at the base of the bladder, the prostate is partitioned into zones referred to as the central, peripheral and transitional zones, all of which surround the urethra. Histologically, the prostate is a highly microvascularized gland comprising fairly large glandular spaces lined with epithelium which, along with the seminal vesicles, supply the majority of fluid to the male ejaculate. As an endocrine-dependent organ, the prostate responds to both the major male hormone, testosterone, and the major female hormones, estrogen and progesterone. Testicular androgen is considered important for prostate growth and development because, in both humans and other animals, castration leads to prostate atrophy and, in most cases, an absence of any incidence of prostatic carcinoma.
The major neoplastic disorders of the prostate are benign enlargement of the prostate, also called benign prostatic hyperplasia (BPH), and prostatic carcinoma, a type of neoplasia. BPH is very common in men over the age of 50. It is characterized by the presence of a number of large distinct nodules in the periurethral area of the prostate. Although benign and not malignant, these nodules can produce obstruction of the urethra causing nocturia, hesitancy to void, and difficulty in starting and stopping a urine stream upon voiding the bladder.
In its more aggressive form, malignant transformed prostatic tissues escape from the prostate capsule and metastasize invading locally and throughout the bloodstream and lymphatic system. Metastasis, defined as tumor implants which are discontinuous with the primary tumor, can occur through direct seeding, lymphatic spread and hematogenous spread. All three routes have been found to occur with prostatic carcinoma. Local invasion typically involves the seminal vesicles, the base of the urinary bladder, and the urethra. Direct seeding occurs when a malignant neoplasm penetrates a natural open field such as the peritoneal, pleural or pericardial cavities. Cells seed along the surfaces of various organs and tissues within the cavity or can simply fill the cavity spaces. Hematogenous spread is typical of sarcomas and carcinomas. Hematogenous spread of prostatic carcinoma occurs primarily to the bones, but can include massive visceral invasion as well. It has been estimated that about 60% of newly diagnosed prostate cancer patients will have metastases at the time of initial diagnosis.
Surgery or radiotherapy is the treatment of choice for early prostatic neoplasia. Surgery involves complete removal of the entire prostate (radical prostatectomy), and often removal of the surrounding lymph nodes, or lymphadenectomy. Radiotherapy, occasionally used as adjuvant therapy, may be either external or interstitial using 125I. Endocrine therapy is the treatment of choice for more advanced forms. The aim of this therapy is to deprive the prostate cells, and presumably the transformed prostate cells as well, of testosterone. This is accomplished by orchiectomy (castration) or administration of estrogens or synthetic hormones which are agonists of luteinizing hormone-releasing hormone. These cellular messengers directly inhibit testicular and organ synthesis and suppress luteinizing hormone secretion which in turn leads to reduced testosterone secretion by the testes. In normal prostate, removal of androgenic hormones results in regression of the gland involving apoptosis of more than 60% of the luminal epithelial cells. Although often initially sensitive to removal of androgens, prostate cancer cells eventually lose this response and continue to grow and spread even in the absence of androgenic steroids. Despite the advances made in achieving a pharmacologic orchiectomy, the survival rates for those with late stage carcinomas are rather bleak.
Current therapeutic regimens for metastatic disease typically involve both chemical and surgical androgen ablation, which although has been demonstrated to extend life when compared to untreated patients, almost invariably results in the development of hormone-refractory disease and the demise of the patient. The fundamental concepts upon which current androgen ablation therapy was developed were reported more than 50 years ago by Huggins and Hodges. (Huggins C, et al., Cancer Res. 1:293-297, 1941). These experiments reported the phenomenon in which removal of androgenic steroids by castration resulted in reduced growth and biochemical activities in prostate cancer.
With the advent of molecular biology, various investigators in laboratories have attempted to understand the molecular biology of castration-induced regression of the prostate at a more mechanistic level. The model systems selected almost invariably compared mRNAs produced prior to castration and during castration-induced regression using rat prostate model systems in vivo. These model systems yield gene activities that may be involved in castration-induced regression but could also be involved in activities that are not directly relevant or related to castration-induced regression but were stimulated by removal of androgenic steroids. It is anticipated that only a small fraction of gene activities modulated by steroid withdrawal would indeed be involved in castration-induced regression and, therefore, significant confounding background activity would be seen in these existing model systems. There is therefore a need for a model system in which the androgenic-stimulated gene activities not associated with castration-induced regression, or “background” gene activities, would be normalized. Moreover, a better understanding of the molecular basis of metastasis, in prostate cancer, as well as other forms of cancer, would allow rational efforts toward the development of novel effective anti-metastatic therapy to proceed.
One such advancement in the understanding of the molecular basis of prostate cancer has occurred through the study of p53. It has been shown that there exists a specific and established association between loss of p53 function and prostate cancer metastasis. Recent studies demonstrated that specific p53 mutations are clonally expanded in metastatic prostate cancer (Stapleton, A M. et al., Clin Cancer Res 3, 1389-97, 1997) and that a pattern of aberrant p53 expression in primary tumors, termed “clustered p53 staining,” has significant prognostic value in predicting recurrence following radical prostatectomy (Quinn, D. I. et. al., Cancer Res 60, 1585-94, 2000 and Stapleton, A M. et. al., Cancer 82, 168-75, 1998). It is generally considered that the nature of functional alterations which occur in cells containing p53 mutations specifically facilitates metastatic seeding, survival, and growth at distant metastatic sites. These alterations likely result, in part, from aberrant regulation of genes under the transcriptional control of p53 that have previously been shown to mediate apoptosis (el-Deiry, W. S., Setnin Cancer Biol 8, 345-57, 1998; Miyashita, T. & Reed, S. C., Cell 80, 293-9, 1995; Sheikh, M S. et. al., Cancer Res 58, 1593-8, 1998; Oda, K. et. al., Cell 102, 849-62, 2000; and Zhu, J. & Chen, Mol Cell Biol 20, 5602-18, 2000) and anti-angiogenic activities (Dameron, K. M., Volpert, O. V., Tainsky, M. A. & Bouck, N., Science 265, 1582-4, 1994; Lopez-Ocejo, 0. et. al., Oncogene 19, 4611-20, 2000; Zou, Z. et. al., J Biol Chem 275, 6051-4, 2000; Zhang, M., Volpert, O., Shi, Y. H. & Bouck, N., Nat Med 6, 196-9, 2000; and Zhang, Y., Griffith, E. C., Sage, S., Jacks, T. & Liu, J. O., Proc Natl Acad Sci USA 97, 6427-32, 2000).
Surprisingly, it has been discovered that certain proteins related to testes-specific, vespid and pathogenic proteins (“RTVP-related” or “RTVP-like” proteins), are up-regulated by p53 in mouse prostate cancer cells. Proteins which are Related to Testes-specific, Vespid and Pathogenic proteins include those proteins with homology to mammalian testes-specific proteins (e.g. TPXI), plant pathogenesis-related proteins (e.g. PR-protein such as subtype 1, PR-lb), vespid venom allergan proteins (antigen 5), or combinations thereof. Homology means that there is a relevant degree of similarity in the amino acid sequence between a polypeptide of the invention and one or more of the proteins mammalian testes-specific proteins, plant pathogenesis proteins and vespid venom allergan antigen 5, or in the respective gene sequences. Relevant homology means that the degree of amino acid sequence similarity is about 35% or greater, preferably about 45% or greater, more preferably about 60% or greater, and even more preferably about 75% or greater. Homology can be determined directly by sequencing the polypeptide of interest and comparing it with the known sequence, or experimentally by methods well know to those or ordinary skill in the art. Homology can be determined using, for example, blastp queries at default settings for amino acid homology determinations, and using blastn queries at default settings for nucleic acid homology determinations.